When looking up valid accounts by name, LookupAccountName returns
a SID and a case-correct domain name. However, the name was input
and LookupAccountName is case-insensitive, so the name is not
necessarily written the same way as in SAM or AD.
Fix that by doing a reverse lookup on the just fetched SID. This
fetches the account name in the correct case. Override the
incoming name with the case correct name from LookupAccountSid.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>